.graph {
    display: block;
    border: #e5e5e5 solid 1px;
    float: none;
    margin: 0 auto;
    height: 500px;
    position: relative;
}

.circle {
    position: absolute;
    background-color: #000;
    width: 20px;
    height: 20px;
    border-radius: 50%;
}

.circle-text {
    position: relative;
    color: white;
    text-align: center;
    z-index: 1;
}

.link {
    border: 1px solid #000;
    position: absolute;
    height: 1px;
    transform-origin: 0 0 0; 
}

.link:hover .link-text {
    display: block;
}

.link-text {
    display: none;
    text-align: center;
}